1. Field of Invention
The present invention relates to covers for molten metal cars, More particularly, the present invention concerns an apparatus for removing and installing a cover from a transfer car having liquid metal contained therein.
2. Description of Prior Art
Transfer cars to move molten metals between processing stations in a steel mill or foundry are well known. One problem related with this transportation system is the heat lost by the molten metal during transportation. If the liquidized metal cools below certain points, the metal may, at a minimum, solidify within the car. Short of solidifying, an alloy contained therein could undergo structural change that my adversely affect the metal.
One method of addressing this problem is to add additional heating furnaces along the processing line. The furnaces could then ensure that thermal loss is not so substantial as to affect the molten metal. However, such additional furnaces add to the processing time and cost.
A less costly alternative is to cover the opening of the transport car. Since the greatest thermal loss occurs through the opening in the top of the car, a cover over this area will preserve the heat within the metal and the transfer car when empty.
One problem associated with covers is the removal of the cover from the transport car when the car is carrying molten metal. Physical removal of the cover by workers exposes them to the dangers of the elevated temperatures associated with molten metal. To utilize powered equipment, such as a crane, is often impractical. Since many noxious and some toxic fumes are produced during the metal processing procedure, draft hoods are deployed along the processing line to draw these fumes safely away These hoods, however, limit the amount of over-head space available for the removal of the covers and, thus, negate the efficacy of a crane.
One device known for removal of covers from transfer cars with limited overhead space is taught in U.S. Pat. No. 5,002,635, which issued Jun. 11, 1991, to Scriven and entitled "REMOVABLE COVER FOR A HOT METAL TRANSFER CAR". Scriven teaches an apparatus formed integrally with a transfer car comprising a track extending from the platform of the transfer car to the opening on its top. A carriage, movably attached to the track, is transported by a power source, such as a motor connected to a drive chain, along the track. The carriage is joined to the cover, such that the cover is deployed over the opening or drawn away from it by the movement of the carriage.
While offering an improvement over the prior art, the Scriven device depends upon motorized Dower means for its operation. Failure of this power means will hamper the entire processing of the metal. Additionally, the cover could be caught while transported within the track, again preventing deployment or withdrawal thereof.
What is needed is an apparatus that can effect movement of the cover without reliance on a mechanical power source. Further, what is needed is an apparatus that can remove a cover from a transport car without the possibility of entrapping the cover and preventing movement thereof. It is to these goals that the present invention is directed.